Simulation of formation temperature of dunites from Kingashsky ultramafic massif (north-western part of Eastern Sayan)

• Published in: Izvestiâ Tomskogo politehničeskogo universiteta. Inžiniring georesursov Vol. 326; no. 8
• Main Authors: Alexey Yurichev, Alexey Chernyshov
• Format: Journal Article
• Language: Russian
• Published: Tomsk Polytechnic University 01.05.2019
• Subjects: chromospinelide; equilibrium crystallization; geothermometer; Kingashsky massif; olivine; temperature regime
• ISSN: 2500-1019; 2413-1830

Relevance of the work is caused by the need of detailed petrological studies of numerous potentially mineralized ultramafic and maficultramafic massifs of the Kan block of the Eastern Sayan to improve the correlation of regional schemes, and to identify Pt-Cu-Ni mineralization in them. One of these massifs - Kingashsky massif, including eponymous large Pt-Cu-Ni deposit, discovered in Soviet time, is the subject of this study. However, despite the increased interest of researchers to this massif, there are unresolved issues on the depth of its formation, comagmatic ultramafic and mafic rocks and conditions of formation and localization of ore in it. The main aim of the study is to assess temperatures of formation of cumulative dunites in Kingashsky ultramafic massif applying known in geological literature olivine-chromospinelide geothermometers. The methods used in the study: petrographic characteristics of rocks on the polarizing microscope AxioScope Carl Zeiss, chemical composition of minerals on the scanning electron microscope Сamscan, equipped with energy-dispersive and wave-dispersive spectrometers. The results. Temperature conditions of formation of cumulative dunites in Kingashsky ultramafic massif through existing versions of olivine-chromospinelide geothermometers are simulated. The estimated equilibrium crystallization of cumulative dunites from massif corresponds to temperatures 1135...1300 °C. At the same time the calculated range of reduced temperatures on geothermometers of Jackson-Irvine-Roeder and Fabries, equal 600... 700 °C, reflects temperatures of mediumtemperature metamorphism of epidote-amphibolite facies, imposed on these rocks, which is widely manifested in the Kan block of Eastern Sayan.